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  1. 1. ENZYMES <ul><li>made of proteins </li></ul><ul><li>biological catalysts (speed up reactions) </li></ul><ul><li>act on molecules (substrate) to break them down/build them up </li></ul><ul><li>most enzymes’ names end in –ase </li></ul>
  2. 2. Anatomy of an enzyme
  3. 3. How Enzymes Work <ul><li>Induced Fit Model </li></ul><ul><li>Active site on enzyme draws substrate(s) closer (attracted by functional gp) </li></ul><ul><li>Active site shaped to only bind to a specific substrate(s), like lock and key </li></ul><ul><li>Sub(s) get drawn into cleft of enzyme </li></ul><ul><li>Once bound, Enzyme-Substrate Complex (ES Complex) is formed. </li></ul>
  4. 4. <ul><li>ES Complex changes shape slightly either breaking or binding sub. molecule(s) </li></ul><ul><li>End product released and enzyme returns to original shape, able to bind more sub. </li></ul><ul><li>YouTube - Enzyme </li></ul>
  5. 5. Activation Energy <ul><li>the amount of energy (without enzymes) needed to start a reaction (usually high) </li></ul><ul><li>enzymes lower amnt of activation energy needed </li></ul>
  6. 6. Enzyme Co-factors <ul><li>non-protein component of enzymes </li></ul><ul><li>help enzyme to catalyze by binding to active site or substrate </li></ul><ul><li>2 types: </li></ul><ul><ul><li>Co-enzymes – organic molecules </li></ul></ul><ul><li>- ex. NAD + (vitamin B derivative) </li></ul><ul><ul><li>Inorganic Ions – ex. Ca 2 +, Zn 2 +… </li></ul></ul>
  7. 7. Enzyme Inhibitors <ul><li>Inhibit (slow down/stop) enzyme activity </li></ul><ul><li>This prevents build up of wastes in cell </li></ul><ul><li>2 kinds: </li></ul><ul><li>Reversible - controls enzyme activity by action on either substrate or end product </li></ul><ul><li>Irreversible – permanently destroys active site </li></ul>
  8. 8. Reversible Enzyme Inhibitors <ul><li>3 types </li></ul><ul><li>Competitive Inhibitor – binds to active site to prevent substrate from binding </li></ul><ul><li>Video: enzyme (biochemistry) :: Competitive inhibitors prevent enzymes from catalyzing with substrates -- Britannica Online Encyclopedia </li></ul>
  9. 9. <ul><li>ii) Noncompetitive Inhibitor – binds somewhere other than active site, causes enzyme to change shape and slow down reaction </li></ul><ul><li>Tutorial 6.1 Enzyme Catalysis </li></ul><ul><li>iii) Allosteric Enzyme Inhibitor – binds to enzyme somewhere other than active site, causing enzyme to change shape and stops reaction </li></ul><ul><li>Tutorial 6.2 Allosteric Regulation of Enzymesl </li></ul>
  10. 10. Irreversible Enzyme Inhibitors <ul><li>permanently destroys active site </li></ul><ul><li>ex. Some heavy metals like Hg, Cd, Pb, As </li></ul>
  11. 11. Regulation of Enzyme Activity <ul><li>Feedback Inhibition </li></ul><ul><ul><li>a product formed in a sequence of reactions inhibits an enzyme that catalyzes a substrate earlier in the reaction </li></ul></ul><ul><ul><li>inhibitor binds to enzyme, slowing down production (non-competitive inhibitor) </li></ul></ul><ul><ul><li>as production slows down, amount of inhibitor available decreases until used up </li></ul></ul><ul><ul><li>so enzyme can start binding and producing again </li></ul></ul>
  12. 12. <ul><ul><li>soon amount of inhibitor in product increases enough to inhibit production again </li></ul></ul><ul><ul><li>continues in a constant loop to control the reaction </li></ul></ul><ul><ul><li>Feedback Inhibition of Biochemical Pathways </li></ul></ul><ul><ul><li>2. Location of Enzyme </li></ul></ul><ul><ul><li>some enzymes kept in cellular compartments until needed </li></ul></ul>